The Calendar

Roman Mars:
This is 99% invisible. I’m Roman Mars.

Roman Mars:
30 days hath September, April, June, and November. February has 28 alone. All the rest have 31, except in leap year. That’s the time when February’s days are 29. That doesn’t even rhyme.

Avery Trufelman:
Oh, the poem I grew up with was slightly different.

Roman Mars:
Producer Avery Trufelman.

Avery Trufelman:
30 days hath September, April, June, and November. All the rest have 31, except for February, which has 28 days clear, and 29 in each leap year. Okay, I think that rhymes actually worse.

Roman Mars:
Both poems say the same thing, which is that months don’t make any logical sense.

Avery Trufelman:
A month is hardly a unit of measurement. It can be anywhere from 28 to 31 days. Sometimes it’s four weeks, sometimes five, sometimes six. You have to buy a new calendar with new dates every single year.

Roman Mars:
It’s a strange design.

David Ewing Duncan:
Well, the year that we now have, and basically consider almost a writ of God – you know, somehow it’s just indivisible, there it is – actually has had an amazing history.

Avery Trufelman:
That is David Ewing Duncan.

David Ewing Duncan:
And I am the author of ‘Calendar: Humanity’s Epic Struggle to Determine a True and Accurate Year.’ The calendar that the world really uses right now is mostly a sort of joining of the Roman calendar and the Egyptian calendar. It’s basically when Caesar and Cleopatra were kind of hanging out and doing their thing.

Roman Mars:
Which is to say, when Roman Caesar and Egyptian Cleopatra were having a torrid love affair.

Avery Trufelman:
This was before Cleopatra got together with Mark Antony. She was 21, and Caesar was 52. But they got together, and they did what lovers do: Discuss the true nature of the Earth’s rotation.

David Ewing Duncan:
And Egyptians, long before the Greeks came, actually discovered the true length of the year.

Roman Mars:
365 days.

Avery Trufelman:
And the Egyptians knew about the length of the year, because of the Nile River.

David Ewing Duncan:
They had something called a nilometer.

Roman Mars:
It was basically a series of steps that went into the Nile.

David Ewing Duncan:
The Nile actually flooded at the same height, virtually every year on the same day. They would just simply mark each year when it hit its height.

Roman Mars:
But the Egyptians also figured out that the year isn’t always exactly 365 days, so they added an extra day every four years, just to make sure that the calendar matched up with the seasons. In other words, they invented the leap year.

Avery Trufelman:
And this was all fantastic news to Caesar because he had a feeling that the Roman calendar wasn’t quite right.

Roman Mars:
The Roman calendar year at the time was around 354 days long.

David Ewing Duncan:
Obviously, that’s a few days short, right? So 11 days, about, short, from the actual solar year.

Avery Trufelman:
And when you lose 11 days year after year after year after year, the seasons start to drift. There’s spring in the winter months, winter in the fall months.

Roman Mars:
And those 11 days were missing because the Roman calendar had always been based on moon cycles.

Avery Trufelman:
Cleopatra inspired Caesar to switch to a calendar that would be consistent with the Earth’s cycle around the sun.

David Ewing Duncan:
When Caesar returned to Rome from his dalliance with Cleopatra, he introduced the Leap Year, which is called the Julian Calendar.

Roman Mars:
Julius Caesar also added back those 11 missing days.

Avery Trufelman:
And the Julian Calendar was instituted throughout the Roman Empire. Which is to say, throughout much of the world. But it was still a bit off.

David Ewing Duncan:
The Julian Calendar wasn’t entirely accurate itself. It was about 11 minutes, 14 seconds off each year. Eventually, we were losing days, and then there was a week, and by 1582, Pope Gregory the 13th had the wherewithal to say, “Okay. We have an inaccurate calendar. We’re worshiping all of our holy days on the wrong day from what they originally were.”

Avery Trufelman:
And with a few small adjustments to realign the year with the seasons, we have the Gregorian calendar, named after Pope Gregory.

Roman Mars:
And that’s what’s on your wall, or your phone.

David Ewing Duncan:
We all use it. We don’t think about it now. And for that reason, there has not been a huge momentum to try to change things. I mean, we basically live with it. But there are a lot of smart people out there, have been for centuries, that have come up with better calendars, and there are better calendars.

Avery Trufelman:
One example of calendar redesign came after the French Revolution. The French decreed the first year of the revolution was the year one, and they made the week 10 days long.

Roman Mars:
This was actually instituted for over a decade, then Napoleon put the kibosh on that when he became emperor.

Avery Trufelman:
And later, another Frenchman created the so-called positivist calendar.

Mark Byrnes:
The positivist calendar was created in 1849 by Auguste Comte.

Roman Mars:
He reorganized the months and renamed them after the great minds of history.

Mark Byrnes:
Moses, Homer, Aristotle, Archimedes, Caesar, Saint Paul-

Avery Trufelman:
All the great white men of history.

Mark Byrnes:
Charlemagne, Dante, Gutenberg, Shakespeare.

Avery Trufelman:
That’s Mark Byrnes, by the way.

Mark Byrnes:
My name is Mark Byrnes. I am the Visual Editor for CityLab.

Avery Trufelman:
That positivist calendar didn’t really take off. It was mostly meant as an inspirational memorial to glorify great thinkers, and, you know, patriarchy. However, there was another radical attempt at calendar reform that actually kind of happened.

Roman Mars:
And Mark Byrnes wrote a piece about it for CityLab.

Mark Byrnes:
I wrote ‘The Death and Life of the 13-Month Calendar.’

Roman Mars:
This was a highly rational 13-month calendar, meant to appeal not to romantics, but to industrialists.

Avery Trufelman:
Because the wonky, weirdly divided Gregorian calendar was difficult for accountants, who had to track monthly numbers, and for the people who had to make the trains run on time. And Moses B. Cotsworth was both of those people.

Mark Byrnes:
Moses B. Cotsworth was an analytics guy, mostly working in the railway industry.

Avery Trufelman:
Cotsworth was a British railwayman, and he was all about efficiency. The Gregorian calendar wasn’t cutting it for him.

Mark Byrnes:
So, let’s say there’s a month where there’s an extra Monday, or there’s a month with an extra Saturday. That would throw off the numbers from month to month. That kind of frustrated Cotsworth, so he created his 13-month calendar.

Roman Mars:
In 1902, Cotsworth presented a design for a calendar of 13 months, where every month was exactly 28 days – no more, no less. Four perfect weeks.

Avery Trufelman:
And this meant that dates were all standardized, as well. You’d always know that the 5th was a Thursday, no matter the month. The 1st was always a Sunday. The 10th was always a Tuesday.

Mark Byrnes:
There’d be a Friday the 13th every single month.

Roman Mars:
Rational railwaymen were not superstitious, clearly.

Avery Trufelman:
All the month names would stay the same, and then that additional month, another 28 even days, would fall between June and July. This additional month would be called Sol.

Roman Mars:
S-O-L.

Mark Byrnes:
Sol, standing for the month where the summer solstice occurs.

Roman Mars:
And the leap year day would be added at the end of Sol, not February, so every four years, Sol would have 29 days.

Avery Trufelman:
All right. So, 28 days times 13 months is 364 days in a year. That is one day less than the actual solar year of 365. So to make it 365, Cotsworth added a new holiday right before the New Year.

Mark Byrnes:
There’s an extra day at the end of the year, called Year Day.

Roman Mars:
And Year Day was just a floating day, not part of any particular month, and it would be a sort of global sabbath.

Avery Trufelman:
Aside from Year Day, all other vacations would be moved to a Monday.

Mark Byrnes:
Holidays would always be practiced or observed on Mondays. You don’t have to worry about certain months where everyone’s out on a Wednesday, and maybe since they have Wednesday off, they want to schedule a Thursday and Friday off.

Roman Mars:
None of that nonsense. Holidays would all be three day weekends. No Wednesdays off.

Avery Trufelman:
Cotsworth pitched his perfect calendar around the United States, giving talks about its myriad benefits, but he couldn’t find many takers. Except for one of the wealthiest and most successful businessmen of that time, George Eastman.

Roman Mars:
George Eastman, the founder of Kodak.

Kathy Connor:
Mr. Eastman had a lot of unique interests, in addition to his company and his philanthropic work. But this, I have to say, is probably one of the weirdest interests that he had and pursued.

Avery Trufelman:
Kathy Connor is the curator of the George Eastman House and Collection in Rochester, New York.

Kathy Connor:
When he had an interest in anything, he always put a decent amount of money into getting other people to buy into his ideas as well, and he did exactly that with the 13-month calendar.

Roman Mars:
Eastman basically took it upon himself to promote Cotsworth’s calendar design, and he started a Calendar League Headquarters in Rochester, in Kodak’s office.

Kathy Connor:
He gave a little office to this calendar reform group, and it was there that they published and printed some different flyers to hand out to local businesses.

Avery Trufelman:
They actually convinced a few local businesses to switch to a 13-month calendar.

Roman Mars:
Including, of course, Mr. Eastman’s own company.

Kathy Connor:
They adapted it at the Eastman Kodak Company in 1924, and they continued to use it until 1989. So, they had it 65 years.

Roman Mars:
Let me just repeat that they used this calendar until 1989.

Avery Trufelman:
Apparently, employees found it useful.

John Cirocco:
When I did sales reporting programs, I didn’t have to worry about, “Well, this is a 28-day month. This is a 31-day month. This is a 30-day month. I acclimated it very quickly.”

Avery Trufelman:
John Cirocco worked at Kodak from 1986 to 1992, and he actually liked the calendar so much that he tried to bring it with him beyond Kodak.

John Cirocco:
A couple of times, I’ve actually tried getting companies that I’ve worked for to go and use a 13-period ( four weeks times 13) calendar.

Roman Mars:
But like Moses Cotsworth and George Eastman before him, John Cirocco just couldn’t convince other businesses to take it on.

Avery Trufelman:
That said, even within Kodak, Eastman couldn’t fully institute the 13-month calendar in its truest form. The calendar as John knew it was kind of a modified version.

John Cirocco:
I only knew it as this was the financial calendar of the Eastman Kodak company.

Roman Mars:
Kodak employees didn’t observe Sol or Year Day, or change every holiday to a Monday.

Avery Trufelman:
It was like how some bankers work in quarters, or some schools function in semesters. Kodak’s internal schedule was organized into 13 periods, just called period 1 to period 13.

John Cirocco:
Instead of saying that today was March 6th, we would say that today is the third period, day three.

Roman Mars:
They used the 13-month calendar as an organizational tool, for planning finances and production schedules.

John Cirocco:
We programmed and we wrote and we designed applications to work within the Kodak 13 periods, but we still lived our life the way the normal Gregorian calendar was.

Avery Trufelman:
Because, of course, the rest of the world was still on the Gregorian calendar. Renaming and reorganizing the days and holidays would have been a total drag.

Roman Mars:
And this is basically the same reason why it would be so hard for the larger world to adopt a 13-month calendar.

Mark Byrnes:
The explanation for how July 4th would work is kind of like the perfect example of how complicated it would be to mentally adjust to this new calendar.

Roman Mars:
That’s journalist Mark Byrnes again.

Avery Trufelman:
Okay, so on the 13-month calendar schedule, July 4th would have to be moved to a Monday, like all the holidays. So then-

Mark Byrnes:
It would really be July 2nd.

Roman Mars:
But when you add in Sol, and shuffle the dates around accordingly, that actual day on the solar calendar wouldn’t fall in July anymore.

Avery Trufelman:
It would actually be Sol 17. But that falls on a Tuesday, so again, you’ve got to make that a Monday, so it would end up as Sol 16.

Mark Byrnes:
So, there’s nothing as patriotic as celebrating Sol 16.

Avery Trufelman:
This is why the calendar, in its truest, most regulated form, couldn’t’ fully work at Kodak. I mean, you have to give your employees a vacation on July 4th, even if it’s not on a Monday. So, random holidays and off days persisted.

Roman Mars:
George Eastman knew that if he wanted to standardize the calendar, Kodak couldn’t do it alone. He would have to convince the rest of the world to make the switch.

Kathy Connor:
He and Mr. Cotsworth, they went to bat a few times in front of a lot of different committees at Congress and in our government, to try to just explain the rationale.

Avery Trufelman:
And this was taken completely seriously.

Mark Byrnes:
Calendar reform became an actual issue of debate for the League of Nations.

Roman Mars:
The League of Nations, as in the precursor to the U.N.

Mark Byrnes:
There are 185 plans before the League of Nations to look at for calendar reform, and Cotsworth and Eastman’s proposal was one of the few finalists.

Avery Trufelman:
Even after George Eastman passed away in 1932, the League of Nations continued discussing calendar redesign.

Mark Byrnes:
Basically, League of Nations couldn’t come to a consensus, and then the rise of Hitler and World War II made it thoroughly unimportant to them. Then the League of Nations folded.

Roman Mars:
Hitler ruins everything. And we just haven’t really considered calendar reform since. Perhaps because when designing time and the way people operate, you have to consider custom and culture. It has to be done entirely and completely, or not at all. So, who knows? Perhaps if everyone decided to adopt it, a regimented calendar could really work better for finances and planning.

Avery Trufelman:
But on the other hand, I think it’s kind of fascinating that our year is not perfectly regimented. It’s out of our control. Sometimes your birthday is on a Tuesday. Sometimes it’s a Saturday. The Gregorian calendar is this organic instrument that ebbs and flows with the seasons and the rotation of the Earth. God, I’ve spent too much time in California.

David Ewing Duncan:
It’s really a bizarre anomaly of history, that this calendar that started with Caesar and Cleopatra, that was reformed by a pope. It was really the Christian calendar… it’s now the calendar of the world.

Roman Mars:
And all we have to help us remember it is a stupid rhyme, that doesn’t even rhyme. By the way, we talked to another longtime Kodak employee for this story.

Robert Shanebrook:
Yes. My name is Robert Shanebrook. I worked for Kodak for 35 years.

Roman Mars:
Robert wrote a book about how Kodak film was made, called ‘Making Kodak Film.’ Its manufacturing process used to be top secret, but Robert got insider access to Kodak’s facilities.

Robert Shanebrook:
I spent 40 days photographing in the factory, like 165 photographs that show all the equipment, and explains the process.

Roman Mars:
This is like its own separate episode. Check it out, nerds. It’s makingkodakfilm.com.

  1. I’ve got an idea for a calendar…it’s named after me: the Curtesian Calendar. Composed of twelve 28-day months and a 13th, 29-day month called “Curtuary” (Curtuary would have 30 days on a leap year). This would be perfect because having perfect 4-week months would be really easy and convenient for business and remembering on what day of the month things will happen for that year…think about it.

  2. Heidi

    I would totally vote for Calendar Reform!

    I would love to see 12 months, with 3 weeks 10 days/week and a bonus 5 day holiday it would make math so much easier. (But the calendar proposed would probably be an easier sell what with the major religions being attached to the 7 day week)

  3. Kelli

    I have always recited the calendar poem as:

    30 Days hath September,
    April, June and November.

    All the rest have 31,
    except for February which is minus some.

    A few years ago I was curious if I was reciting it correctly, looked up and figured the traditional recitation maybe more accurate, but mine has a better rhythm. ;)

  4. you can also use your knuckles to find out how many days a month has. start on your index or pinky knucle and mark a month for every knuckle bump and a month for every groove in between fingers. a bump is a 31 day month, a groove is a 30 day month. when you reach the end of your knuckles just go back to the first one and that will be 31 days again.

  5. J

    Even as a Rochester native with parents, aunts, uncles, cousins etc who worked for Kodak at one point, I had NEVER heard about this before. Great episode this week!

  6. Alex

    Ahh, the flat circle.

    “I think it was dad.”

    Priceless. Thanks for another great episode.

  7. Jane

    The Aussie rhyme I was taught rhymes, I’m 31 and I still run through it in my head to check the days!

    30 days has September, April, June and November
    31 the others date excepting February 28.
    But in leap year we assign, February 29!

    Boom!

    Love the podcast 99, keep it up!

  8. Dylan

    The sarcastic throwaway line of “all the great white men of history” really added nothing to the story, as evidenced by it’s omission from this transcript.

    There is certainly a time and a place for race and gender as a subject in regards to design, but it’s insertion into this piece seemed unnecessary and off putting.

    I hope future episodes take greater consideration to such broad statements regarding race and gender.

  9. joe

    Why does she have to throw in her random 2 cents about patriarchy? It was not really the time or place for that discussion. Kind of a non sequitur.

  10. Hunter

    I spent nine years designing and building calendars for a publishing company, and rebuilding them every . . . single . . . year, so this episode really spoke to me and I’ve had too much opportunity to think about this. While there are 14 possible permutations for a calendar year, there are 28 possible permutations for the structure of a month, though each month only has seven (and February has 14). Ugh! What always seemed odd was the alternating long-short pattern that is disrupted by July and August consecutively having 31 days. I figured that the alternating pattern should continue (so August would now have 30 days, September 31, etc.) and that extra day could go to February so it would have 29/30. We could even continue with leap years. But that would be too easy!

  11. Another rhyme that doesn’t rhyme:

    30 days hath September, April, June, and November
    All the rest have 31
    Except, quite contrary, is that February
    Which has 28 most of the time, but in leap year 29

  12. Sam

    How I learned the lengths of the months:

    Thirty days hath September, April, June and November.
    All the rest have 31, except February which has 28.
    And leap year coming once in four, always gives it one day more.

    I think the “28” part is intentionally meant to be a clunker, in that it doesn’t rhyme and is also the odd one out. Also “one day more” isn’t so prescriptive, but oh well.

  13. Daisy

    Great episode…but looking globally would have made it better. Ethiopia (and large parts of Eritrea) has used a 13 month calendar for centuries: it has twelve 30-day months, plus a 5-6 day long thirteenth month for timekeeping purposes. Hence, the great tourism tagline “13 Months of Sunshine!” The Ethiopian year begins on September 11 of the Gregorian calendar, and is seven years behind it (i.e., 2014 Gregorian = 2007 Ethiopian). Imagine the fun when you have to submit Ethiopian travel receipts to an American university for reimbursement!!

  14. Tiffany

    I’ve spent the last 8 years following a 13 period fiscal calendar at work,and I love it. It just makes so much sense!
    Unfortunately we run into the same issues as Kodak, holidays move around and we have to “re-set” our year to the calendar year with a “leap week” every few years.
    Also, it matches up nicely with a 28 day birthcontrol cycle which is super handy.

  15. Diederik

    Very informative and interesting article. I work for Marriott International and until a few years ago we also worked on a 13 period calendar. One of the main advantages of the 28 day periods was having the same number of weekdays. Different days have very different demand patterns at hotels and having 4 Tuesdays vs. 5 Tuesday in a month can have dramatic affects on performance.

  16. Andreas

    In Swedish it does rhyme:

    30 dagar har september, april, juni och november
    28 en allen (28 one only)
    Alla de övriga trettioen (all the others thirty-one)

    But then again you have to remember which is the short one. You cant win them all.

  17. Colin

    The next step to this analysis would be to examine the way the days themselves are divided – the use of 24 hours (sometimes as 24, sometimes divided into 12 +12), 60 minutes, 60 seconds.
    Then there is the way we present dates in different parts of the world – Month/Day/Year; Day/Month/Year; Year/Day/Month.

  18. AlongComesASpider

    30 days hath September
    April, June and November
    All the rest have 31
    Except for February, alone
    With 28, rain or shine
    And on leap year? 29

  19. karen jean

    30 days hath September
    April, June and November
    Except for February which we’ve assigned
    A leap year which makes it 29.

  20. karen jean

    … that’s what we were taught in grammar school; misses that February otherwise is 28 but works for me.

  21. pamela farmer

    Apropos of calendars, and your upcoming presentation, your demographic includes this 55 year old. I guess I’m that invisible part…. Also, I share Dylan’s sentiment, that the bit about “all the great white men of history.” Off putting. Not all of us have drunk the feminist kool-aid, and that kind of politicking seems unnecessary in a podcast about design.

  22. Darren

    We sang the calendar rhyme in primary school

    30 days has September
    April June and November
    when short February’s done
    all the rest have 31

    .d

  23. Ana

    Hello everyone! Roman, I loved this episode. 99% invisible is the perfect resource for interesting conversations. I am from Spain and for as long as I can remember, we count the days in each month using our knuckles. It’s like having a calendar whisperer installed in your body. I found this youtube video that explains the system: https://www.youtube.com/watch?v=p6Ma0D-fN38

    Enjoy!

  24. Keely

    The rhyme I was taught was:

    30 days hath September,
    April, June and November.
    When short February’s done,
    all the rest have 31.

  25. Jamie Cox

    When I was working as a software engineer it was customary to make a comment in code citing the governing document, usually a Military Standard, ANSI Standard, ISO standard, Internet IRC, etc. I wrote some code which had to deal with the months and computing leap year. (I must be like the 10,000th programmer to do this.) I looked and looked for an official source for this. I ended up citing Pope Gregory XIII’s 1582 papal bull “Inter Gravissimas”. It seems that the United States never officially adopted the Gregorian calendar! The constitution make several references to specific dates, but no indication is given which calendar is to be used to determine those dates. The US government has laws and standards for everything — except this. It seems that since the conversion to the Gregorian calendar had already happened when the US split away from the British empire, no formal adoption was necessary. I find this state of affairs completely amazing. Here’s something we all use every day, for all government and civil functions, but it has never been officially codified — we use the calendar we use simply by tradition and common usage. I’m perfectly happy with this situation. I’m glad that there are some areas where government regulation is apparently not necessary. If anyone knows of a US or international standard that deals with how leap year is to be computed other than “Inter Gravissimas”, I would like to hear about it.

  26. 30 days hath September,
    April, June and November
    All the rest have 31,
    Except for February – it has no fun
    28 days does it just fine,
    Except for leap year – it has 29

    Thanks to my excellent 2nd grade teacher, Ms. Younkman.

  27. Lanada

    I’d like to add to the Knuckle System mentioned in an earlier comment. Make a fist with one hand, back of the hand towards you, and notice the peaks and valleys of your knuckles and the spaces in between.

    Starting on the knuckle of your index finger, start naming the months as you touch knuckle (January,) space (February,) knuckle (March,) space (April) etc. When you get to your 5th finger knuckle, tap it twice (that’s July and August) and come back across your hand: space (September,) knuckle (October) etc.

    All the months which land on peaks have 31 days, all the spaces have 30 days (or 28/29 for poor old February.) I use this every time I need to remember the number of days in a month.

  28. I enjoyed the episode, but you make it seem as if Kodak’s calendar is bizarre and unique. It’s not. I work on analytics and reporting software for business, and many of our customers – especially those in retail and manufacturing – use a 4-4-5 calendar for reporting (or 4-5-4, or 5-4-4). This calendar has 13-week quarters comprised of two four-week periods and a five-week period. Thus you end up with a 364-day year, and so an additional week is added every few years. I think Kodak’s “Year Day” would be a better solution, with an extra “Year Day” every leap year perhaps.

    Anyway, my main point is that this reporting calendar structure is not unique to Kodak nor even that uncommon.

  29. Haoran

    Great episode. I find calendars fascinating.

    Some interesting things that I felt could have been added to the episode : why do days start at midnight, when in the middle east, and in the Jewish system, days start at sundown?

    What about lunar calendar systems that persist? The Chinese calendar is still somewhat observed; the diaspora Chinese communities of the world still celebrate Chinese new year, which is calculated by lunar calendar.

    Same as the Persian New Year, the Arabic new year, the Nepali new year, etc.

  30. Adnan

    What’s the song in around 10 min mark?!
    it appears in many episodes and I have looked for it in the music credits list, and couldn’t find it.

    Great episode BTW!

  31. Cookpod

    Just listened to this podcast – the 13 month year also doesn’t work for Sol as the summer solstice is in December in the southern hemisphere

  32. Trevor M

    “Sometimes a month is four weeks long, sometimes five, sometimes six.”

    It’s only ever six weeks “long” if you have a weird definition of weeks.

    1. Trevor M

      Also, claiming that the summer solstice would happen in the month of Sol… gee thanks, on behalf of the southern hemisphere that sounds tremendously biased.

Leave a Reply

Your email address will not be published. Required fields are marked *

All Categories

Playlist